This invention relates to a data transfer apparatus, and more particularly, to a data transfer apparatus which uses a telecommunication control technique in the Internet.
As a result of increasing expansion of infrastructure for telecommunication networks, transfers of video data, sound data, and the like are now often performed through the telecommunication networks in addition to conventional data transfers for web browsing, email exchange, and the like. Of those, the transfer of video data is also performed through multicast scheme. As compared with the transfer for web browsing and email exchange, in the transfer of video data and sound data, a user is greatly affected by a disturbance in data transfer (e.g., delay in data transfer). Thus, a network having high fault tolerance is required. As a method of enhancing fault tolerance of a network, there are provided a method of enhancing fault tolerance in a data transfer apparatus constituting a network, a method of enhancing fault tolerance of the data transfer apparatus as a constituent element of the network, and a method of enhancing fault tolerance of the network.
One method of enhancing fault tolerance in the data transfer apparatus involves, for example, separating a transfer system and a control system and making those systems redundant (see, for example, “AX7800S/AX5400S Software Reference Manual Vol. 2”, ALAXALA Networks Corporation By separating the transfer system and the control system to make operations thereof independent of each other, data transfer can be continued even when a failure occurs in the control system.
An example of the method of enhancing fault tolerance of data transfer apparatuses as a constituent element of the network is a method of constructing a single virtual data transfer apparatus which is made redundant by a plurality of data transfer apparatuses. As means for constructing the virtual data transfer apparatus as described above, there are a VRRP (see, for example, “Virtual Router Redundancy Protocol (VRRP)”, RFC3768, April 2004), a GSRP (see, for example, “AX7800S/AX5400S Software Manual Reference Manual Vol. 2”, ALAXALA Networks Corporation and an HSRP (see, for example, “Cisco Hot Standby Router Protocol (HSRP)”, RFC2281, March 1998).
In the virtual data transfer apparatus composed of the plurality of data transfer apparatuses, each of the data transfer apparatuses is classified into an active status for actually transferring data or a standby status that does not transfer data. A standby system (i.e., the data transfer apparatus of the standby status) transfers data in place of an active system (i.e., the data transfer apparatus of the active status) when a failure occurs in the active system. In general, each of the data transfer apparatuses exchanges path control information which indicates how received data is to be transferred, with the data transfer apparatus adjacent thereto, and constantly updates the information. When the standby system is switched to a new active system at the time of failure of the (ex-) active system, in order for the new active system to perform data transfer in the similar manner as the ex-active system, the standby system needs to hold path control information similar to that of the ex-active system. As a method for the standby system to hold the path control information similar to that of the active system, there is a method in which a standby system also receives information that is received by an active system for creating path control information (see, for example, JP 2003-143193 A), and a method of transferring path control information from an active system to a standby system (see, for example, JP 2001-186182 A).
As a method of enhancing fault tolerance as the network, there is a method of providing a plurality of paths from one data transfer apparatus to another data transfer apparatus in a network, for example. At a time of failure of the one data transfer apparatus, a path that runs through the data transfer apparatus is switched to a path that detours around the data transfer apparatus, whereby data transfer is continued. A failure detection of the data transfer apparatus and an update of the path control information are carried out by path control protocols such as BGP, OSPF, and IS-IS (see, for example, “OSPF for IPv6”, RFC2740, December 1999). In addition, each path control protocol provides a method of quickening restoration after detecting a failure in the data transfer apparatus, called a graceful restart.